1 //===- IRSymtab.cpp - implementation of IR symbol tables ------------------===//
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //===----------------------------------------------------------------------===//
9 #include "llvm/Object/IRSymtab.h"
10 #include "llvm/ADT/ArrayRef.h"
11 #include "llvm/ADT/DenseMap.h"
12 #include "llvm/ADT/SmallPtrSet.h"
13 #include "llvm/ADT/SmallString.h"
14 #include "llvm/ADT/SmallVector.h"
15 #include "llvm/ADT/StringRef.h"
16 #include "llvm/ADT/Triple.h"
17 #include "llvm/Bitcode/BitcodeReader.h"
18 #include "llvm/Config/llvm-config.h"
19 #include "llvm/IR/Comdat.h"
20 #include "llvm/IR/DataLayout.h"
21 #include "llvm/IR/GlobalAlias.h"
22 #include "llvm/IR/GlobalObject.h"
23 #include "llvm/IR/Mangler.h"
24 #include "llvm/IR/Metadata.h"
25 #include "llvm/IR/Module.h"
26 #include "llvm/MC/StringTableBuilder.h"
27 #include "llvm/Object/IRObjectFile.h"
28 #include "llvm/Object/ModuleSymbolTable.h"
29 #include "llvm/Object/SymbolicFile.h"
30 #include "llvm/Support/Allocator.h"
31 #include "llvm/Support/Casting.h"
32 #include "llvm/Support/CommandLine.h"
33 #include "llvm/Support/Error.h"
34 #include "llvm/Support/StringSaver.h"
35 #include "llvm/Support/VCSRevision.h"
36 #include "llvm/Support/raw_ostream.h"
43 using namespace irsymtab;
45 cl::opt<bool> DisableBitcodeVersionUpgrade(
46 "disable-bitcode-version-upgrade", cl::init(false), cl::Hidden,
47 cl::desc("Disable automatic bitcode upgrade for version mismatch"));
49 static const char *PreservedSymbols[] = {
50 #define HANDLE_LIBCALL(code, name) name,
51 #include "llvm/IR/RuntimeLibcalls.def"
53 // There are global variables, so put it here instead of in
54 // RuntimeLibcalls.def.
55 // TODO: Are there similar such variables?
62 const char *getExpectedProducerName() {
63 static char DefaultName[] = LLVM_VERSION_STRING
68 // Allows for testing of the irsymtab writer and upgrade mechanism. This
69 // environment variable should not be set by users.
70 if (char *OverrideName = getenv("LLVM_OVERRIDE_PRODUCER"))
75 const char *kExpectedProducerName = getExpectedProducerName();
77 /// Stores the temporary state that is required to build an IR symbol table.
79 SmallVector<char, 0> &Symtab;
80 StringTableBuilder &StrtabBuilder;
83 // This ctor initializes a StringSaver using the passed in BumpPtrAllocator.
84 // The StringTableBuilder does not create a copy of any strings added to it,
85 // so this provides somewhere to store any strings that we create.
86 Builder(SmallVector<char, 0> &Symtab, StringTableBuilder &StrtabBuilder,
87 BumpPtrAllocator &Alloc)
88 : Symtab(Symtab), StrtabBuilder(StrtabBuilder), Saver(Alloc) {}
90 DenseMap<const Comdat *, int> ComdatMap;
94 std::vector<storage::Comdat> Comdats;
95 std::vector<storage::Module> Mods;
96 std::vector<storage::Symbol> Syms;
97 std::vector<storage::Uncommon> Uncommons;
99 std::string COFFLinkerOpts;
100 raw_string_ostream COFFLinkerOptsOS{COFFLinkerOpts};
102 std::vector<storage::Str> DependentLibraries;
104 void setStr(storage::Str &S, StringRef Value) {
105 S.Offset = StrtabBuilder.add(Value);
106 S.Size = Value.size();
109 template <typename T>
110 void writeRange(storage::Range<T> &R, const std::vector<T> &Objs) {
111 R.Offset = Symtab.size();
112 R.Size = Objs.size();
113 Symtab.insert(Symtab.end(), reinterpret_cast<const char *>(Objs.data()),
114 reinterpret_cast<const char *>(Objs.data() + Objs.size()));
117 Expected<int> getComdatIndex(const Comdat *C, const Module *M);
119 Error addModule(Module *M);
120 Error addSymbol(const ModuleSymbolTable &Msymtab,
121 const SmallPtrSet<GlobalValue *, 4> &Used,
122 ModuleSymbolTable::Symbol Sym);
124 Error build(ArrayRef<Module *> Mods);
127 Error Builder::addModule(Module *M) {
128 if (M->getDataLayoutStr().empty())
129 return make_error<StringError>("input module has no datalayout",
130 inconvertibleErrorCode());
132 // Symbols in the llvm.used list will get the FB_Used bit and will not be
133 // internalized. We do this for llvm.compiler.used as well:
135 // IR symbol table tracks module-level asm symbol references but not inline
136 // asm. A symbol only referenced by inline asm is not in the IR symbol table,
137 // so we may not know that the definition (in another translation unit) is
138 // referenced. That definition may have __attribute__((used)) (which lowers to
139 // llvm.compiler.used on ELF targets) to communicate to the compiler that it
140 // may be used by inline asm. The usage is perfectly fine, so we treat
141 // llvm.compiler.used conservatively as llvm.used to work around our own
143 SmallVector<GlobalValue *, 4> UsedV;
144 collectUsedGlobalVariables(*M, UsedV, /*CompilerUsed=*/false);
145 collectUsedGlobalVariables(*M, UsedV, /*CompilerUsed=*/true);
146 SmallPtrSet<GlobalValue *, 4> Used(UsedV.begin(), UsedV.end());
148 ModuleSymbolTable Msymtab;
149 Msymtab.addModule(M);
152 Mod.Begin = Syms.size();
153 Mod.End = Syms.size() + Msymtab.symbols().size();
154 Mod.UncBegin = Uncommons.size();
157 if (TT.isOSBinFormatCOFF()) {
158 if (auto E = M->materializeMetadata())
160 if (NamedMDNode *LinkerOptions =
161 M->getNamedMetadata("llvm.linker.options")) {
162 for (MDNode *MDOptions : LinkerOptions->operands())
163 for (const MDOperand &MDOption : cast<MDNode>(MDOptions)->operands())
164 COFFLinkerOptsOS << " " << cast<MDString>(MDOption)->getString();
168 if (TT.isOSBinFormatELF()) {
169 if (auto E = M->materializeMetadata())
171 if (NamedMDNode *N = M->getNamedMetadata("llvm.dependent-libraries")) {
172 for (MDNode *MDOptions : N->operands()) {
173 const auto OperandStr =
174 cast<MDString>(cast<MDNode>(MDOptions)->getOperand(0))->getString();
175 storage::Str Specifier;
176 setStr(Specifier, OperandStr);
177 DependentLibraries.emplace_back(Specifier);
182 for (ModuleSymbolTable::Symbol Msym : Msymtab.symbols())
183 if (Error Err = addSymbol(Msymtab, Used, Msym))
186 return Error::success();
189 Expected<int> Builder::getComdatIndex(const Comdat *C, const Module *M) {
190 auto P = ComdatMap.insert(std::make_pair(C, Comdats.size()));
193 if (TT.isOSBinFormatCOFF()) {
194 const GlobalValue *GV = M->getNamedValue(C->getName());
196 return make_error<StringError>("Could not find leader",
197 inconvertibleErrorCode());
198 // Internal leaders do not affect symbol resolution, therefore they do not
199 // appear in the symbol table.
200 if (GV->hasLocalLinkage()) {
201 P.first->second = -1;
204 llvm::raw_string_ostream OS(Name);
205 Mang.getNameWithPrefix(OS, GV, false);
207 Name = std::string(C->getName());
210 storage::Comdat Comdat;
211 setStr(Comdat.Name, Saver.save(Name));
212 Comdat.SelectionKind = C->getSelectionKind();
213 Comdats.push_back(Comdat);
216 return P.first->second;
219 Error Builder::addSymbol(const ModuleSymbolTable &Msymtab,
220 const SmallPtrSet<GlobalValue *, 4> &Used,
221 ModuleSymbolTable::Symbol Msym) {
223 storage::Symbol &Sym = Syms.back();
226 storage::Uncommon *Unc = nullptr;
227 auto Uncommon = [&]() -> storage::Uncommon & {
230 Sym.Flags |= 1 << storage::Symbol::FB_has_uncommon;
231 Uncommons.emplace_back();
232 Unc = &Uncommons.back();
234 setStr(Unc->COFFWeakExternFallbackName, "");
235 setStr(Unc->SectionName, "");
239 SmallString<64> Name;
241 raw_svector_ostream OS(Name);
242 Msymtab.printSymbolName(OS, Msym);
244 setStr(Sym.Name, Saver.save(Name.str()));
246 auto Flags = Msymtab.getSymbolFlags(Msym);
247 if (Flags & object::BasicSymbolRef::SF_Undefined)
248 Sym.Flags |= 1 << storage::Symbol::FB_undefined;
249 if (Flags & object::BasicSymbolRef::SF_Weak)
250 Sym.Flags |= 1 << storage::Symbol::FB_weak;
251 if (Flags & object::BasicSymbolRef::SF_Common)
252 Sym.Flags |= 1 << storage::Symbol::FB_common;
253 if (Flags & object::BasicSymbolRef::SF_Indirect)
254 Sym.Flags |= 1 << storage::Symbol::FB_indirect;
255 if (Flags & object::BasicSymbolRef::SF_Global)
256 Sym.Flags |= 1 << storage::Symbol::FB_global;
257 if (Flags & object::BasicSymbolRef::SF_FormatSpecific)
258 Sym.Flags |= 1 << storage::Symbol::FB_format_specific;
259 if (Flags & object::BasicSymbolRef::SF_Executable)
260 Sym.Flags |= 1 << storage::Symbol::FB_executable;
262 Sym.ComdatIndex = -1;
263 auto *GV = Msym.dyn_cast<GlobalValue *>();
265 // Undefined module asm symbols act as GC roots and are implicitly used.
266 if (Flags & object::BasicSymbolRef::SF_Undefined)
267 Sym.Flags |= 1 << storage::Symbol::FB_used;
268 setStr(Sym.IRName, "");
269 return Error::success();
272 setStr(Sym.IRName, GV->getName());
274 bool IsPreservedSymbol = llvm::is_contained(PreservedSymbols, GV->getName());
276 if (Used.count(GV) || IsPreservedSymbol)
277 Sym.Flags |= 1 << storage::Symbol::FB_used;
278 if (GV->isThreadLocal())
279 Sym.Flags |= 1 << storage::Symbol::FB_tls;
280 if (GV->hasGlobalUnnamedAddr())
281 Sym.Flags |= 1 << storage::Symbol::FB_unnamed_addr;
282 if (GV->canBeOmittedFromSymbolTable())
283 Sym.Flags |= 1 << storage::Symbol::FB_may_omit;
284 Sym.Flags |= unsigned(GV->getVisibility()) << storage::Symbol::FB_visibility;
286 if (Flags & object::BasicSymbolRef::SF_Common) {
287 auto *GVar = dyn_cast<GlobalVariable>(GV);
289 return make_error<StringError>("Only variables can have common linkage!",
290 inconvertibleErrorCode());
291 Uncommon().CommonSize =
292 GV->getParent()->getDataLayout().getTypeAllocSize(GV->getValueType());
293 Uncommon().CommonAlign = GVar->getAlignment();
296 const GlobalObject *GO = GV->getAliaseeObject();
298 if (isa<GlobalIFunc>(GV))
299 GO = cast<GlobalIFunc>(GV)->getResolverFunction();
301 return make_error<StringError>("Unable to determine comdat of alias!",
302 inconvertibleErrorCode());
304 if (const Comdat *C = GO->getComdat()) {
305 Expected<int> ComdatIndexOrErr = getComdatIndex(C, GV->getParent());
306 if (!ComdatIndexOrErr)
307 return ComdatIndexOrErr.takeError();
308 Sym.ComdatIndex = *ComdatIndexOrErr;
311 if (TT.isOSBinFormatCOFF()) {
312 emitLinkerFlagsForGlobalCOFF(COFFLinkerOptsOS, GV, TT, Mang);
314 if ((Flags & object::BasicSymbolRef::SF_Weak) &&
315 (Flags & object::BasicSymbolRef::SF_Indirect)) {
316 auto *Fallback = dyn_cast<GlobalValue>(
317 cast<GlobalAlias>(GV)->getAliasee()->stripPointerCasts());
319 return make_error<StringError>("Invalid weak external",
320 inconvertibleErrorCode());
321 std::string FallbackName;
322 raw_string_ostream OS(FallbackName);
323 Msymtab.printSymbolName(OS, Fallback);
325 setStr(Uncommon().COFFWeakExternFallbackName, Saver.save(FallbackName));
329 if (!GO->getSection().empty())
330 setStr(Uncommon().SectionName, Saver.save(GO->getSection()));
332 return Error::success();
335 Error Builder::build(ArrayRef<Module *> IRMods) {
338 assert(!IRMods.empty());
339 Hdr.Version = storage::Header::kCurrentVersion;
340 setStr(Hdr.Producer, kExpectedProducerName);
341 setStr(Hdr.TargetTriple, IRMods[0]->getTargetTriple());
342 setStr(Hdr.SourceFileName, IRMods[0]->getSourceFileName());
343 TT = Triple(IRMods[0]->getTargetTriple());
345 for (auto *M : IRMods)
346 if (Error Err = addModule(M))
349 COFFLinkerOptsOS.flush();
350 setStr(Hdr.COFFLinkerOpts, Saver.save(COFFLinkerOpts));
352 // We are about to fill in the header's range fields, so reserve space for it
353 // and copy it in afterwards.
354 Symtab.resize(sizeof(storage::Header));
355 writeRange(Hdr.Modules, Mods);
356 writeRange(Hdr.Comdats, Comdats);
357 writeRange(Hdr.Symbols, Syms);
358 writeRange(Hdr.Uncommons, Uncommons);
359 writeRange(Hdr.DependentLibraries, DependentLibraries);
360 *reinterpret_cast<storage::Header *>(Symtab.data()) = Hdr;
361 return Error::success();
364 } // end anonymous namespace
366 Error irsymtab::build(ArrayRef<Module *> Mods, SmallVector<char, 0> &Symtab,
367 StringTableBuilder &StrtabBuilder,
368 BumpPtrAllocator &Alloc) {
369 return Builder(Symtab, StrtabBuilder, Alloc).build(Mods);
372 // Upgrade a vector of bitcode modules created by an old version of LLVM by
373 // creating an irsymtab for them in the current format.
374 static Expected<FileContents> upgrade(ArrayRef<BitcodeModule> BMs) {
378 std::vector<Module *> Mods;
379 std::vector<std::unique_ptr<Module>> OwnedMods;
380 for (auto BM : BMs) {
381 Expected<std::unique_ptr<Module>> MOrErr =
382 BM.getLazyModule(Ctx, /*ShouldLazyLoadMetadata*/ true,
383 /*IsImporting*/ false);
385 return MOrErr.takeError();
387 Mods.push_back(MOrErr->get());
388 OwnedMods.push_back(std::move(*MOrErr));
391 StringTableBuilder StrtabBuilder(StringTableBuilder::RAW);
392 BumpPtrAllocator Alloc;
393 if (Error E = build(Mods, FC.Symtab, StrtabBuilder, Alloc))
396 StrtabBuilder.finalizeInOrder();
397 FC.Strtab.resize(StrtabBuilder.getSize());
398 StrtabBuilder.write((uint8_t *)FC.Strtab.data());
400 FC.TheReader = {{FC.Symtab.data(), FC.Symtab.size()},
401 {FC.Strtab.data(), FC.Strtab.size()}};
402 return std::move(FC);
405 Expected<FileContents> irsymtab::readBitcode(const BitcodeFileContents &BFC) {
406 if (BFC.Mods.empty())
407 return make_error<StringError>("Bitcode file does not contain any modules",
408 inconvertibleErrorCode());
410 if (!DisableBitcodeVersionUpgrade) {
411 if (BFC.StrtabForSymtab.empty() ||
412 BFC.Symtab.size() < sizeof(storage::Header))
413 return upgrade(BFC.Mods);
415 // We cannot use the regular reader to read the version and producer,
416 // because it will expect the header to be in the current format. The only
417 // thing we can rely on is that the version and producer will be present as
418 // the first struct elements.
419 auto *Hdr = reinterpret_cast<const storage::Header *>(BFC.Symtab.data());
420 unsigned Version = Hdr->Version;
421 StringRef Producer = Hdr->Producer.get(BFC.StrtabForSymtab);
422 if (Version != storage::Header::kCurrentVersion ||
423 Producer != kExpectedProducerName)
424 return upgrade(BFC.Mods);
428 FC.TheReader = {{BFC.Symtab.data(), BFC.Symtab.size()},
429 {BFC.StrtabForSymtab.data(), BFC.StrtabForSymtab.size()}};
431 // Finally, make sure that the number of modules in the symbol table matches
432 // the number of modules in the bitcode file. If they differ, it may mean that
433 // the bitcode file was created by binary concatenation, so we need to create
434 // a new symbol table from scratch.
435 if (FC.TheReader.getNumModules() != BFC.Mods.size())
436 return upgrade(std::move(BFC.Mods));
438 return std::move(FC);